Voltage-compensating transformer



Patented Sept. 26, 1939 2,173,905

UNITED STATES PATENT OFFICE VOLTAGE COMPENSATING TRANSFORMER Walter Kalbskopf, Nuremburg, Germany, assignor to Suddeutsche Apparate-Fabrik G. in. b. H., Nuremburg, Germany, a company Application May 28, 1937, Serial No. 145,396 In Germany May 30, 1936 6 Claims. (Cl. 1'75363) Electric rectifying systems, especially those acttransformer. This requirement considerably ing with the aid of metal dry-rectifiers, are freadds to the expense for such rectifying devices. quently expected to produce direct current po- Furthermore, on account of the complicated vectentials which in the case of load variations shall torial dependence of the voltages of both trans- 5 vary only within comparatively narrow limits. former and regulating choke such rectifying de- If rectifying devices are not provided with vices cannot be calculated but for distribution voltage-controlling means, the direct voltage will mains of a definite voltage. In fact, it is not poswith increasing load considerably decrease on sible to arrange for connecting such devices to account of the drop of potential across the rectidifferent mains-voltages by joining them to diffying valves. ferent taps of the transformer and choke. Also Diverse devices and circuit arrangements are it is not possible correctly to design the Winding known by which an automatic voltage compensaof such regulating choke. On the contrary, each tion is obtained in dependence on the demand choke must be adjusted separately after having upon the rectifier. For instance, it is known to been connected to the apertai transformer employ regulating chokes the primary of which and rectifying valve. is connected in series with the primary or the The hitherto known regulating transformers secondary of. a transformer supplying the rectilikewise have disadvantages. Either a plurality fying valve and through the secondary of which of transformers are necessary or the voltage comthe utilization current flows. These chokes are pensation obtained is imperfect and does not 00- gradually saturated with the utilization current Cur W n the necessary t s being due 20 increasing. The voltage drop across the primary to the dispersion in the secondary Winding. of the regulating choke consequently decreases Th s d dva a s are d d y the inven- While the voltage at the transformer increases by tiOIl described hereinafter y y Of p the same amount, thus compensating the in- The invention enables an ideal voltage compensareased potential drop at the rectifying valve. tion to be obtained With the aid of one trans- 25 By properly dimensioning the regulating choke former, as will be understood from the following it is possible to balance the device in such a mandescripti n, reference being ha to, th mnor that the direct potential at the receiveror D y drawing in Which utilization-apparatus shall be constant whether Figs. 1 to 5 are wiring d s each Showing the load increase or decrease. one embodiment of the invention. 30

Also, devices are known in which the voltage Each of the arrangements p e e in Figscompensation occurs at the transformer itself. 1 t0 4 as a three-legged iron ore o t e kind In the known compensation transformers the priused in t e-p se transformers W le the armary, the secondary and the magnetising windrengement represented in 5 has Wo s h ing are coiled around separate cores of the transres- The l s ther f are i na ed I. II, III. 85 former. The voltage regulation is here obtained A source of the alternating currents to be rectiin such a way that the magnetising winding fied, which is denoted by the sign is connected flown through by the direct current controls the o a 01 1 Wh s the primary Of t Vo emagnetic flux in the secondary winding and compensating transformer. The secondary there hence also controls the voltage of this winding. f C ns sts of a mai W nd SI a d a allXili ry 40 By connecting two magnetising windings in op- W ding 82. The windings sl, 8?! are disposed on position to each other it will in a well known different legs, winding 8! being coiled around the manner be possible in connection with regulating leg fitt d t e p y 1 and e interconchokes and also with regulating transformers to neeted in Opposition to h Ot er- G denotes a prevent an alternating current component from l'eetifierm, h designate direct Curr nt 45 entering the utilization circuit, and this can be COilS p s d 0n the s II, I

attained without annulling the magnetising ef- These parts a i t r n ted in the manfect of these windings. her that appears from the drawing.

The known voltage-regulating devices for rec- In h rr m n wn in Fig. pr m ry 2 tifier arrangements have several disadvantages and winding 8! are coiled around leg I while the so which are obviated by the inv nti n windings m, s2 are arranged on leg II. Leg III As regards the provision of a regulating choke, has no winding. these disadvantages are as follows. In the first In the condition of no load no current flows in place, in order to obtain a voltage-regulation a coil m, this being included in the utilization circhoke coil must be provided in addition to the cuit. Part of the alternating flux produced by 55 the primary p is acting on the counter-winding $2. The energy thus inducted in this winding decreases the secondary voltage which would be applied to rectifier G by winding si alone, that is, if this winding were not counter-acted by winding $2.

In the state of full load leg II is magnetically saturated or highly magnetised by the coil m. As a result the alternating flux component that before has been acting on the winding s2 is completely or almost completely caused to now through leg III. The counter-voltage before induced in the winding 82 disappears or decreases accordingly, the voltage effective at rectifier G thus increasing.

In this way the counter-action of the winding 82 is controlled by the utilization circuit and with the aid of the coil m in such a manner that within the limits determined by the conditions of no load and full load there shall be applied to the rectifier that voltage in. each case which is necessary in order to compensate for variations which occur in the utilization circuit.

Since coil m is likewise acted upon by the alternating flux an alternating current component will be transferred to the direct current side. If it is desired to avoid this, two such transformers, each of half power, may be inter-connected by connecting their coils m in series in such a manner that the alternating voltage components shall neutralize each other. Such an arrangement is illustrated in Fig. 5, the operation being essentially like that of Fig. 1.

By providing the primary p with taps the transformer is easy to connect to different mains voltages. This is not possible in the case of regulating chokes. By selectively connecting the primaries of two transformers either in parallel or in series these may be connected to two different mains voltages without taps being required and without the necessity for a surplus expenditure of copper. Due to the fact that with the novel arrangement the correlation of the individual values of the alternating current is not of vectorial nature the. transformer windings are comparatively easy to calculate so as to do away with the troublesome adjusting necessary in the case of regulating chokes.

A device according to the invention may be used with a rectifier associated with a resistance load and is adapted also for compensating batteries and further suitable for charging storage batteries or accumulators. Experiments have shown that in the case of resistance load 2. volt age consistency of 12% is easy to obtain even under unfavorable conditions. Also it has been found by experiments that there is within wide limits an approximately proportional relation between the direct current increase and alternating voltage increase. In the case of battery compensation the starting and stoppage oi the charging current may be made to occur within very narrow limits of the battery voltage, as between cell potentials of from 2.2 to 2.4 volts, for example.

The arrangement shown in Fig. 1 also allows of quickly charging a buffer battery from time to time. In order to perform this, the coil in or winding 52 or parts of these have to be shortcircuited.

If the arrangement disclosed in Fig. l is to be used for the charging of a storage battery then instead of coil m two coils ml, m2 are disposed on leg II, as represented in Fig. 2, ml being connected to the charging voltage While m2 is included in the charging circuit and in this regard is equivalent to coil m, Fig. 1. The coils ml, m2 are arranged to oppose each other.

In the state of no load, Fig. 2, only coil ml carries direct current, thus magnetising leg II to such extent that no alternating voltage can be induced in the winding 82. Therefore the undiminished voltage of the winding 5! is now applied to rectifier G. When, however, the battery to be charged is cut in, coil m2 too carries the charging current and thus acts to neutralize the magnetising effect of coil mi. The alternating fiux now also flows through leg II, thus inducing an alternating voltage in winding 32. The voltage at rectifier G hence decreases for the reasons stated. The arrangement is such that when connecting the battery the charging current has its maximum intensity. If now during the charging the intensity of the charging current decreases under the action of the increasing counter-voltage of the battery, then the influence of the coil ml will predominate. As a result, leg II is magnetised so as to decrease the voltage induced in winding 82, thus increasing proportionally the voltage induced in winding sl,

whereby the charging current is given its original strength. In this way the charging current will act with its full intensity until the charging has been finished.

In the arrangement shown in Fig. 3 the primary p and winding sl are disposed on leg II. Winding s2 and a direct current coil m?. are arranged on leg I. Leg III carries a direct current coil mi and a. direct current coil it that forms a large number of turns of thin wire and is arranged to act in opposition to coil ml.

The action of the coils 1), s s2 is the same as before described. In the state of no load, only coil it carries direct current. By coil h the leg III is magnetically saturated. Hereby the alternating flux produced by the primary p is prevented from entering the leg III. A component of this alternating flux is therefore active in leg I. In the state of load, however, coils ml, m2 too carry the direct current. Coil ml in the case of full load therefore acts to neutralize the magnetising effect of the coil h. Coil m2, however magnetises the leg I and thus causes the magnetic flux produced by coil 13 to flow into leg III. The number of the lines of force in leg I, and hence the voltage in winding 82 is hereby decreased. Consequently the alternating voltage applied to rectifier G increases accordingly, being the difference of the voltages produced in the windings st, 32. in a manner quite similar to the systems described with reference to Figs. 1 and 2. The alternating voltages induced in the coils ml, m2 neutralize each other, because these are interconnected in opposition to each other.

The arrangement represented in Fig. 4 similarly to that shown in Fig. 2 serves to charge storage batteries. For this purpose the coil it is not disposed on leg III, as in the case of Fig. 3, but is disposed on leg I.

When here the maximum charging current is flowing through such battery, the magnetising eifect of coil h is neutralized by the countercoil m2 while coil ml acts to highly magnetise leg III. The primary alternating flux is hereby caused to flow in leg I instead of leg III. Consequently the alternating voltage in winding 32 increases so that the alternating voltage resulting from the co-operation of sl and s2 and applied to rectifier G is small. If now the counter- This arrangement thus acts voltage of the battery rises, the charging current tends to decrease. As a result, the magnetising effect of coil h will predominate again while in leg III the magnetisation eifected by coil ml is diminished. Therefore the magnetic lines of force are caused to flow into leg III instead of leg I. The alternating voltage produced in winding 32 consequently decreases, whereby as before described the alternating voltage effective at rectifier G is raised. The coils or windings of the transformer are so calculated that the increasing battery voltage is compensated by the increasing rectifier voltage, the charging current being kept constant in this way.

What is claimed is:

1. A voltage compensating arrangement com prising in combination with a utilization circuit an alternating current source, a three-legged iron core, a primary coil connected to this current source and disposed on one leg of said core, a main secondary winding coiled around this leg, an auxiliary secondary winding coiled around another leg of the said core and connected in opposition to the main secondary, a rectifier connected to said secondary windings, a direct current coil disposed on the second said leg, connected to said rectifier and included in the utilization circuit.

2. A voltage compensating arrangement according to claim 1, further comprising a second core similar to said core first mentioned and having a similar set of coils and windings similarly connected, the two different current coils being interconnected in opposition to each other.

3. A voltage compensating arrangement comprising in combination with a utilization circuit an alternating current source, a three-legged iron core, a primary winding connected to this current source and disposed on one leg of said core, a main secondary winding coiled around said one leg, and an auxiliary secondary winding coiled around a second leg of the said core and connected in opposition to the main secondary, a rectifier connected to said secondary windings, a first direct current coil on the said second leg, at second direct current coil arranged on the third leg, and an additional direct current coil on said third leg and joined to said second direct current coil in opposition to it, these three direct current coils being connected to said rectifier, and said first and second coils being serially included in the utilization circuit.

4. An arrangement according to claim 3, wherein the first and second said direct current coils are interconnected in opposition to each other.

5. A voltage compensating arrangement comprising in combination with a utilization circuit an alternating current source, a three-legged iron core, a primary coil connected with this current source and disposed on one leg of said core, a main secondary winding coiled around this leg, an auxiliary secondary winding coiled around a second leg of the said core and connected to the main secondary in opposition to it, a direct current coil on this second leg, a direct current coil arranged on the third leg, and an additional direct current coil on the said second leg, and a rectifier included in the utilisation circuit serially with the two first said direct current coils, said additional direct current coil being connected across to the direct current terminals of the rectifier.

6. A voltage compensating arrangement according to claim 1 having a second direct current coil in addition to the said direct current coil and disposed on the same leg, these two coils being connected in opposition to each other, and said second direct current coil being connected across the direct current terminals of said rectifier.

WALTER KALBSKOPF. 

